An enterprise application archive (EAR) can consist of many sub modules. The sub modules can be web modules (WAR), ejb modules (JAR), resource adapter modules (RAR) or application client modules (jar). When an EAR consist of many sub modules, the deployment plans for all the sub modules can be provided in a single file named geronimo-application.xml. This single file contains the deployment details of each of the sub modules of the EAR. Alternatively, each of the sub modules can package its corresponding deployment plan file within itself. However, the preferable way is to provide a single deployment plan through geronimo-application.xml for all the sub modules. This mechanism provides flexibility of allowing us to modify the deployment configuration for all modules through a single file. In this section, we explore EAR deployment plan and understand what it contains.

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There are 3 places a deployment plan (partial) can be associated with an ear, and they are used in this order:

So, anything in an external plan takes precedence over bits in (2) or (3) configuring the same module. Anything in (2) takes precedence over a module level plan. If a module level plan is missing from (1) its looked for in (2),then (3); if missing from (1) and (2), then its looked for in the module (3).

There is no attempt to merge plans from these different locations: e.g. if there's something in (1) for a module, any other plans are ignored.

An enterprise application archive (EAR) should provide its deployment descriptor in the application.xml file. The application.xml lists all the sub modules in the EAR file along with the descriptions. In addition to the standard deployment descriptor, the EAR should also provide Geronimo specific deployment plan in geronimo-application.xml. Along with the description of each of the sub modules of the EAR file, this file also provides mappings for JEE resources that each of the sub modules refers in their deployment descriptor. The geronimo-application.xml is divided into several sections where in each section, the deployment plan for a sub module is provided. geronimo-application.xml is the highest level plan that provides deployment plan for all sub modules; hence it can contain XML elements from every other Geronimo XML schema used by Geronimo application deployer. The geronimo-application.xml is the super set of all other deployment plans.

For example, following is the structure of an EAR that has a web module and an ejb module.

The Order.ear file shown above contains two modules. One is OrderWEB.war file which is a web module and the other is OrderEJB.jar file which is an ejb module. The META-INF folder in Order.ear contains the application deployment descriptor (application.xml) and the Geronimo application deployment plan (geronimo-application.xml). The web application and the ejb application have packaged only their respective deployment descriptors. But the deployment plans for these modules are provided in the geronimo-application.xml.
The web application (OrderWAR.war) looks up stateless session bean in the OrderEJB.jar module to retrieve the order information. The RetrieveOrderInfoBean in OrderEJB.jar module uses JDBC connection to read the order information from a DB2 database.

The deployment descriptor of the OrderEJB.jar is as follows.

ejb-jar.xml

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The default namespace of the above XML document is http://java.sun.com/xml/ns/javaee. The XML elements that do not have a namespace prefix belong to the default namespace.

In the RetrieveOrderInfoBean, the following code is used to look up the Datasource object and obtain a database connection.

examples.session.stateless_dd.RetrieveOrderInfoBean

The deployment descriptor of the OrderWEB.war is as follows.

web.xml

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The default namespace of the above XML document is http://java.sun.com/xml/ns/javaee. The XML elements that do not have a namespace prefix belong to the default namespace.

In the RetrieveOrder servlet, the following code is used to look up the ejb to retrieve the order details.

examples.web.servlet.RetrieveOrder

The deployment descriptor of the Order.ear is as follows.

application.xml

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The default namespace of the above XML document is http://java.sun.com/xml/ns/javaee. The XML elements that do not have a namespace prefix belong to the default namespace.

Observe how the JEE 5 resource names and ejb names in ejb-jar.xml and web.xml are mapped to actual resources deployed in the server through geronimo-application.xml.

As we can observe from the geronimo-application.xml, the deployment plans for web and ejb modules are wrapped in <module> .... </module> elements. The xml elements used to provide deployment plan for the web module are from the schema http://geronimo.apache.org/xml/ns/j2ee/web-2.0.1 which is the schema for geronimo-web.xml. Similarly, the xml elements used to provide ejb deployment plan are from the schema http://openejb.apache.org/xml/ns/openejb-jar-2.2 which is the schema for openejb-jar.xml. Hence, geronimo-application.xml borrows elements from all other schemas to provide deployment plan for its sub modules.

Also, observe that, in the geronimo-application.xml, along with moduleId configuration for the EAR itself, there is a moduleId configuration for each web and ejb modules. If the above EAR file deployed on the server and the configurations are listed, the following output would be displayed on the console.

The moduleId Order/OrderEAR/5.0/car is the configuration for the Order.ear. The ejb module declares a dependency on the console.dbpool/OrderDS/1.0/rar configuration in <sys:dependencies> section. This is the moduleId of the database pool that connects to the DB2 database where the order details are stored.